The invention relates to a device for adjusting the azimuth of the trajectory of a rotary-drilling bit.
In the case of rotary drilling, the drill bit is brought into rotation by a drill string one end of which located at the surface, is connected to a means for rotationally driving the drill bit.
The thrust load on the tool is also exerted by the drill string.
In current drilling techniques and particularly in oil drilling, there are well-known processes and devices for allowing a carrying out of a certain remote adjustment of the drill bit trajectory.
This adjustment may relate to a drift of the trajectory, with respect to the angle of this trajectory to the vertical or to the azimuth of the trajectory, to the angular position of a vertical drilling plane containing the axis of the hole or well, and/or with respect to a predetermined direction which is preferably the direction of the magnetic north.
The known devices and processes for adjusting the azimuth of the trajectory of a rotary-drilling bit require complex mechanical or electronic means comprising several mobile parts and imposing either a mechanical anchoring of part of the device inside the hole being drilled, or an electronic locating of the adjusting means with respect to the vertical drilling plane containing the axis of the hole or well in the process of being drilled.
The devices of the prior art which are used for adjusting the trajectory of a drill bit comprise means allowing the trajectory to be deflected in the wanted direction, which are connected to the drill string and which comprise bearing surfaces resting on the surface of the hole or wellbore, offset with respect to the drill string. When the means for adjusting the trajectory are set into operation, the bearing surfaces contact the inner surface of a hole in a wanted orientation.
Setting and actuating such adjusting devices is generally complex. It imposes the immobilization of said devices with respect to the wall of the wellbore and involves the use of a downhole motor.